Generally, in plasma welding machines, as a plasma welding gun is provided with an arc ignition device therein, thus the plasma welding has an oversize bulk which is not applicable to use in a small space and, in turns reduce its usage in the plasma welding field. The present invention aims at developing an individual arc ignition device which is cooperated with the plasma welding gun, so as to broaden the usage of the plasma welding machine in the welding field, by which a new energy revolution will be achieved in the plasma welding field.